You cast the Ritual inscribed in the scroll, using the Scroll’s Tier as the caster’s Tier and the number of Proficiency Boosts in any skill required by the ritual to determine any effects of the casting.
Any Components necessary for the ritual to occur (such as those required by a Revivify ritual or to enhance a casting of Craft Illusion) must be present when you activate the Scroll, and are consumed over the course of casting the ritual.
The Actions or time required to cast the ritual from the Scroll is identical to that which would be required to cast the inscribed Ritual normally.
You can craft a Scroll of any ritual you know how to cast, and any ritual that is granted by a Skill Feat that you meet the prerequisites to take, even if you do not possess that feat. You cannot craft a scroll containing the Elemental Gift ritual with this Formula; see the Scroll Of Mage’s Gift page for that purpose.
If a ritual would require one or more Upgrades to function as you intend, you must choose which Upgrade is contained within the Scroll, and the Scroll’s minimum Tier is equal to 1 plus +1 per Upgrade you are inscribing into it.
If a Ritual would require the consumption of Components or other materials to achieve the desired effect, they must be provided by the person activating the Scroll; you do not need to provide them during the crafting process. Many scrolls are sold with the required Components as part of a package for ease of use.
You cannot craft a Tier 0 Ritual Scroll.